DESCRIPTION: This application proposes to study the production of disordered speech by children with Down's syndrome and Specific Language Impairments (SLIs), and to analyze the data obtained using the novel and state of the art techniques of nonlinear dynamics. Separate studies will be done for the two impaired groups. Age-matched and Mean Length of Utterance (MLU)-matched controls will be used in each study. Subjects will be asked to generate dialog stories using puppets and prompted by picture books, during high- and low-demand contexts operationally defined by instructions to "talk fast" or "talk slo." The utterances produced will be analyzed, and ten measures of speaking rate, verbal accuracy, and grammatical complexity derived. Phase portraits will be made of these variables. Trajectories of these measures in phase space will be compared between conditions, and dimensionality of the phase portraits computed to characterize nonlinear attractors underlying the data. These outcomes will be compared with more traditional (3X5 ANOVA) analyses of the same data.